Doctor Who: 5 Best & 5 Worst Creature Designs From The Original Series
Best Creature no. 3: The Cybermen (The Tenth Planet and others)
With their name and appearance it would have been easy to present these metal monsters as robots, but the idea that the silver suits contain something that now barely resembles a human being is chilling. First appearing in 1966 they're almost as old as the Daleks, and have been given a shiny upgrade for the new series. The Tomb of the Cybermen is perhaps one of the spookiest episodes they appear in; the way their mouth clicks open and that emotionless, buzzing voice comes out brings me out in goosebumps every time.
Part of their fear factor is that they once resembled us and have now become something barely human, and unfortunately much of that side of their nature was largely ignored throughout most of the series. They remained fairly threatening in subsequent episodes, with a memorable surprise appearance in Earthshock but for me they had been reduced to a "menacing monster" status which just didn't compare to their old horror.
Tom MacRae did a good job of bringing back this aspect of the Cybermen in 2006, especially by cyber-ising a parallel Jackie Tyler, and the sight of them stomping uniformly down the streets of London during the series finale told the watching whovians that they were officially back in business. Pitching them up against the Daleks resulted in a truly epic battle, though the Cybermen were totally massacred despite outnumbering them several thousand to one, and I hope that the Battle of Canary Wharf (looks even more impressive in capital letters, doesn't it?) will be remembered in the history books for many years to come. Even if it sort of didn't really happen.